The present invention relates to a frame buffer control method and circuit useful in, for example, a page printer.
A page printer has a memory referred to as a frame buffer in which a bit-mapped image of a printed page, or part of a printed page, can be stored. The frame buffer may also be used to store bit maps of characters and symbols. The frame buffer typically comprises dynamic random-access memory (DRAM) devices, which are accessed according to multiplexed row and column addresses output by a frame buffer control circuit.
Many DRAM devices have a mode of operation, referred to as a fast page mode, in which input of a row address is followed by input of multiple column addresses. Fast page mode allows data to be accessed rapidly, as long as the access stays within the same row.
A problem in conventional page printers is that access does not tend to stay in the same row. Even the simple operation of copying the bit map of one character, to place the character on a printed page, typically requires access to several different rows. The operation of the printer is accordingly slowed by the need to switch repeatedly from one row address to another, with attendant delays for activating different rows of memory cells.